T-Mobile's HTC Sensation 4G is the latest phone to suffer from the death grip problem. The death grip problem occurs when one grabs the phone in a certain way, which then results in the phone losing its cellular signal, and its Wi-Fi and Bluetooth connectivity. The problem is caused by the Sensation's back cover according to multiple tests done by Nordic Hardware. The metal battery cover has a few plastic patches that act as antennae for the phone. If you cover up one of the patches, your connectivity will weaken, especially with bluetooth and Wi-Fi.
As seen in the video below, when one puts the device on the palm of their hand, it stops audio playback. The death grip will also block weaker hotspots from showing up on your Sensation. The first reaction of most people to correct this problem is the same as the iPhone, use a phone case. This will not work on the Sensation since it actually blocks the antennae rather preventing the user from shorting it which was the case on the iPhone 4. Not sure how HTC plans on fixing this, but we will keep you updated on the situation.
source: Unwired View